This application claims the priority of German application 196 09 210.8 filed in Germany on Mar. 9, 1996, the disclosure of which is expressly incorporated by reference herein.
This application is also related to commonly assigned U.S. application Ser. No. 08/815,264 filed herewith, based on German application number 196 09 209.4 filed in Germany on Mar. 9, 1996, the contents of which are incorporated by reference thereto.
The invention relates to a shift device for a change speed gearbox having two or more clutches for coupling a gear wheel to a gearbox shaft.
In a shift device of this general type described in German Patent Document DE 41 18 931 A1, the pivotably movable locking element is constructed in the form of a two-armed locking lever which is pivotably mounted on the gearbox casing at a central point located between its two lever ends. On its one lever arm it has a recess for engagement of the linearly movable locking element and interacts with its other lever end by means of a locking cam with a corresponding mating cam contour of the shift rocker, in such a way that the locking cam is held, in the neutral position of the shift rocker corresponding to the disengaged state of the gear wheel clutch, in engagement with the mating cam contour on the shift rocker by means of a restoring spring which acts on the locking lever--and, on the other hand, when the shift rocker is activated into a gear speed position corresponding to the engaged state of the other gear wheel clutch, the locking cam is pivoted by the mating cam contour into its other end position in which it is no longer the recess of the locking lever but rather its locking face which is congruent with the geometric axis for the movements of the linearly movable locking element. When an additional shift rocker is used in this known shift device, a second two-armed locking lever which interacts with the second shift rocker and an intermediate locking linkage which interacts with both two-armed locking levers and also with the first shift rocker must be provided, so that this known shift device requires a complicated design.
German Patent Document DE-A 21 32 736 also discloses a shift device for change speed gearboxes of vehicles having three shift rods to be locked, in which shift device cylindrical spring-loaded locking elements are arranged between the shift rods, the locking elements being axially displaceably secured in a bearing hole of the gearbox casing, and in which shift device the shift rods are arranged in the form of a triangle. In order to be able to lock in each case two shift rods at the same time and only release one for shifting gears--the required shift means and their bearing being easy to manufacture, being arranged in a space-saving fashion and being intended to permit reliable locking--in this known shift locking device the arrangement is effected in such a way that the locking elements are displaceably mounted in a bearing hole, connecting two shift rods, of the gearbox casing, the locking elements being provided with sloping faces at one end in the region of a further locking hole which opens into the bearing hole at a right angle, and a sphere which interacts with the sloping faces of the locking elements being inserted into the locking hole.
Finally, German Patent Document DE 29 30 151 A1 also discloses a change speed gearbox of the countershaft type, in which three shift rods arranged parallel to the gearbox shafts are mounted axially displaceably in a gearbox casing which is connected to a clutch casing using flanges, of which shift rods two are connected fixedly in terms of movement in each case to the fork shaft of an associated linearly movable shift fork and the third is connected in an articulated fashion to the fork shaft of an associated shift fork which is mounted so as to be pivotable in relation to the gearbox casing.
An object on which the invention is based is to provide a shift device of the type mentioned above which is both distinguished by a simple design of the locking mechanism and can be easily extended for use by more than one shift rocker and/or shift rod.
This object is advantageously achieved according to the preferred embodiments of the invention by providing a shifting assembly comprising a first axially displaceable shift rod operable to actuate a first gear wheel clutch, a first pivotably displaceable shift rocker operable to actuate a second gear wheel clutch, a first pivotably movable locking element carried by the first shift rocker, and a first linearly movable locking element extending transversely to, and selectively lockingly engaging with the first shift rod, wherein said first pivotably movable locking element and first linearly movable locking element are configured to assure locking of the first shift rocker against actuation of the second clutch when the first shift rod is actuating the first clutch and locking of the first shift rod against actuation of the first clutch when the first shift rocker is actuating the second clutch.
In the shift device according to the invention, the casing-side pivot bearing and the restoring spring for the pivotably movable locking element are omitted and the precision of the kinematic interaction between the shift rocker and pivotably movable locking element is optimized by a respective arrangement of a pivot bearing.
In the shift device according to the invention, the locking members are brought into effect between the shift rod and shift rocker over the shortest possible path.
Shift devices according to certain preferred embodiments of the invention include locking members which are easily and advantageously adapted to the extension of the shift assembly to include a second shift rocker operable to actuate a third gear wheel clutch and a second pivotably movable locking element carried by the second shift rocker and with corresponding locking elements to effectively control against undesired simultaneous activation of any of the first, second and third clutches.
Shift devices according to certain preferred embodiments of the invention include locking elements which are easily and advantageously adapted to the extension of the shift assembly to include a second axially displaceable shift rod to activate a fourth gear wheel clutch, a second linearly displaceable locking element engageable to lock the second shift rod and with corresponding locking elements to effectively control against undesired simultaneous actuation of any of the first to fourth clutches.
In shift devices constructed according to preferred embodiments of the invention, linearly and pivotably movable locking elements are directly moved into mutual engagement by means of their inclined faces. This engagement is made easier when in each case a sphere is intermediately connected in accordance with especially preferred embodiments of the invention.
In especially preferred embodiments the shifting assemblies include essentially the advantageous refinements of the locking elements, including a locking mechanism casing with accommodates the latter, using sheet-steel stamping technology.
In shift devices constructed according to the invention, no additional shift rods are required for activating or locking the shift rockers.
In shift devices constructed according to the invention, the number of the totality of gear wheel clutches for the gearbox shafts does not preclude utilization of the novel locking assembly arrangement.
In shift devices constructed according to the invention, the number of activation mechanisms of the gear wheel clutches formed by the shift rockers does not preclude utilization of the novel locking assembly arrangement.
In shift devices according to preferred embodiments of the invention, a central shift shaft with a plurality of shift fingers for actuating all the gear wheel clutches may be used--in particular with one shift finger for each of the shift rockers.
In shift devices according to preferred embodiments of the invention, a "spectacle-shaped" end plate arranged in the center of the gearbox bears a central locking mechanism casing in which the movements of all the shift rods and rockers are brought together.
In shift devices according to preferred embodiments of the invention, the locking mechanism casing which accommodates the spheres and locking elements can be suspended, as a premounted physical unit, from an end shield of the gearbox.
In shift devices according to preferred embodiments of the invention, a low-friction support of the forces induced on the gear shift lever by the driver is achieved by resting the shift fingers directly on the shift rockers and thus on the pivots of the rockers with a step-down ratio of the friction moments, caused by the force support, in the ratio bolt radius/radius of engagement.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.